Grid-based three dimensional storage and retrieval systems employing robotic storage/retrieval vehicles are known in the art, including those disclosed in Canadian patent application CA2885984, German patent application DE102009017241, U.S. Pat. No. 8,628,289, U.S. patent application US2014/0031972 and international PCT applications WO201490684 and WO201519055.
The PCT applications disclose systems in which the robotic storage/retrieval vehicles traverse an upper grid supported in an elevated position over a three dimensional array of stacked storage bins, and each vehicle features a lift device that can be lowered down from the vehicle when parked on the grid in a position overlying a selected stack of storage bins, whereby the lifting device carries the storage bin up into a cavity in the underside of the vehicle. CA2885984 discloses a similar system, but in which two different three dimensional arrays are situated one over the other, with a respective fleet of robotic storage/retrieval vehicles traversing a respective grid above each storage array. In these types of systems, while the presence of a respective stack of storage bins at every Cartesian co-ordinate point of the horizontal grid provides a space-efficient storage solution, a potential drawback of such a system is that only the uppermost bin in any stack is directly retrievable any given time. Access to bins further down the stack requires prior removal of the bins above it.
The German reference features an upper two-level storage array, and a lower single-level storage array, and a fleet of robotic storage/retrieval vehicles operating on a gridded track system situated between the upper and lower arrays. The robotic vehicles can access storage bins from not only the lower array, but also from and the lower level of the top array, thereby enabling access to more than just the uppermost bins in the multi-level upper array.
US2015127143 discloses a robotic storage/retrieval vehicle capable of simultaneously lifting multiple storage bins from a stack in a three dimensional storage array, thereby reducing the number of discrete lifting operations required to access a given bin that is buried below two or more of the uppermost bins in the stack. Once upper bins have been removed by this multi-bin vehicle, a conventional single-bin storage/retrieval vehicle can then lift the target bin. A potential drawback is the need for two distinct vehicle types that separately access and then remove the target bin.
US2014/0031972 and U.S. Pat. No. 8,628,289 both avoid the multi-level access problem by employing an aisle-based format, where open aisles between rows of stacked storage locations enable robotic item retrieval from any location, though at the expense of a less space efficient solution, as the open aisles between every two rows take up a significant volume of the overall system space.
U.S. Pat. No. 5,595,263 discloses a single-stack storage and retrieval system in which storage locations at each level of the stack are situated around a hollow central shaft, but retrieval from the storage locations is performed by externally mounted robotic pickers and cooperating elevators that feed a dedicated lower conveyor of the single-column storage array. Other single-stack storage facilities are disclosed in U.S. patent application 2006/0228196, Japanese patent reference JP2003341810 and French Patent FR2614609.
U.S. patent application 2013/0181586 discloses a rotary unit with a plurality of bin holders radially attached to a central shaft for input and output of goods from a computer controlled, robotically served storage system, but provides no improvement to the actual storage layout itself.
U.S. Pat. No. 7,267,518 discloses a conveyor system for collecting and moving material among a two-dimensional array of storage bins, but is only capable of serving a single-level two-dimensional array of storage sites, not a multi-level three-dimensional array.
Accordingly, there remains room for improvements and alternative designs in the field of three-dimensional storage/retrieval systems, and particularly a desire for improved balance between space-efficiency and individual location access within three dimensional storage and retrieval systems.
Applicant has developed a novel storage and retrieval system with a unique combination of features not heretofore seen or suggested in the prior art, and which not only alleviate the forgoing shortcomings of the prior art, but may also provide other advantages or benefits.